SCS therapy is a relatively recent development in which electrical stimulation is applied to the central nervous system in the spinal cord area for the relief of pain of the trunk and/or limbs. Presently, there exist no known techniques for objectively determining the efficacy of an SCS system. Typically, efficacy determinations for SCS systems rely on empirical methods which are based on information conveyed from the patient to clinicians. For example, to assess efficacy a physician will interview a patient and ask simple questions relative, for example, to the level of pain that the patient is or has been experiencing after SCS has been implemented.
Currently, the practice of adjusting or optimizing post-implantation parameters in SCS systems relies exclusively on patient-reported feedback. Patient reporting is subject to the patient's own perception of symptoms. This prevents objective determinations of symptomatic conditions and leaves diagnostic procedures prone to inappropriate assumptions about the existing or potential efficacy of SCS in a given patient. To illustrate the problem, one can imagine a patient being treated with SCS who experiences significant pain reduction. As a result of the reduction in pain, the patient becomes more active, and takes part in day-to-day activities that were not undertaken before SCS treatment. That increase in activity actually causes the patient to experience more pain which may not necessarily be due to the condition treated with SCS, but instead may be the result of the heightened activity level. When asked whether pain has decreased, the patient may very well respond that it has not, even though the SCS may actually be mitigating the pain level. Thus, present efficacy evaluation techniques do not allow for a objective qualification of patient reported data.
It would therefore be desirable to provide a system which enables objective interpretation of subjective information regarding the efficacy of an SCS system. In particular, it would be desirable to provide a system which permits storage and retrieval of an historical representation of objective patient data, including patient activity levels and therapy adjustments to provide a physician with an objective reference to subjective patient information.